New genetic evidence suggests Australia may have been populated by two separate groups of humans - one from Papua New Guinea, the other from Indonesia
But more work is needed to confirm the idea. And not all scientists agree that these latest results shed new light on the long-standing debate on how humans colonised Australia.
Dr Sheila van Holst Pellekaan, a molecular anthropologist from the University of New South Wales in Sydney, will present her research at a Australian Archaeological Association conference in Melbourne next month.
Previous genetic analysis shows that modern humans took two migration routes out of Africa 100,000 to 150,000 years ago, she says.
One group went north into Europe and Northern Eurasia, the other along the coast via Saudi Arabia, India and South-East Asia.
Dr van Holst Pellekaan analysed mitochondrial DNA (mtDNA) from Aboriginal people in western New South Wales and Central Australia.
She says she found evidence of two ancient genetic groups that appear to be linked to these two migration routes.
Dr van Holst Pellekaan says some archaeologists argue there was more than one founding population of Australia, and her research is the first genetic evidence that could be used to support this.
It is possible that some Australians came in from the north via Papua New Guinea and the other took a more southerly route via Indonesia, she says.
Archaeologist Dr Colin Pardoe, who is speaking at the conference on a related topic, disagrees.
He believes the diversity of early Australians could have arisen from one group that came in from South-East Asia and then diversified as it adapted to different environments.
DR Pardoe is not convinced Dr van Holst Pellekaan has identified two founding groups.
"Are these two totally distinct groups that came in or are they representatives of one major group that came in that has all that diversity within it?" he asks.
This is a possibility that Dr van Holst Pellekaan accepts.
"The idea of two founding populations is speculative," she says. "I can't prove it either way."
Dr Pardoe says more DNA samples from other places such as the Indonesian islands and Papua New Guinea would need to be analysed.
"We need to understand the pattern of variation in these large groupings to see where Australians are coming from," he says.
Professor Peter Brown of the University of New England in Armidale also says further data is required, including studies of Y chromosome DNA, as mtDNA only reflects the maternal line.
Dr van Holst Pellekaan says some Y-chromosome studies of Aboriginal people from Central Australia have found a connection with India, but there have been no comprehensive studies of this type.
Dr Van Holst Pellekaan says despite the links with the global lineages that came out of Africa, the Australian groups are quite different from those shown in samples from Papua New Guinea, the Andaman and Nicobar Islands and Malaysia.
"[People] have to have been in Australia for a very long time for that diversity to generate. We're saying at least 40,000 years," she says.
Dr Van Holst Pellekaan accepts the idea of tracing Aboriginal people back to Africa can clash with some cultural beliefs, which she respects.
"I simply present it to them as a scientist's way of seeing how the language groups might have related to each other," she says.
"I can only give them the information I come up with. I don't ask them to believe it."
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